$ { \left[\begin{array}{rrr}{1} & {3} & {1} \\ {-2} & {1} & {2}\end{array}\right]+\left[\begin{array}{rrr}{1} & {4} & {2} \\ {-1} & {0} & {-1}\end{array}\right] = {?} } $
To find the sum of two matrices, add the corresponding items between each matrix. ${\left[\begin{array}{rrr}{1}+{1} & {3}+{4} & {1}+{2} \\ {-2}+{-1} & {1}+{0} & {2}+{-1}\end{array}\right]}$ Now, simplify: ${\left[\begin{array}{rrr}{2} & {7} & {3} \\ {-3} & {1} & {1}\end{array}\right]}$